Conventional barrel shift devices are composed of a multistage selector. On the other hand, for the purpose of improving a throughput in a signal process, there is a need for a barrel shift device which is divided into pipeline registers and in which a shift process is executed in a multistage process stage.
For example, Patent Document 1 discloses a conventional barrel shift device having a multistage selector configuration. The barrel shift device of Patent Document 1 has a structure in which shift circuits composed of a selector which selects, based on a control signal, whether or not a shift is performed are combined in stages. For example, in order to achieve an arbitrary shift ranging from a 15-bit left shift to a 16-bit right shift, shift circuits having 1-bit, 2-bit, 4-bit, and 8-bit left-shift functions, and a shift circuit having a 16-bit right-shift function are combined in stages. In this case, a 5-bit right shift is achieved by activating the 1-bit left-shift circuit, the 2-bit left-shift circuit, the 8-bit left-shift circuit, and the 16-bit right-shift circuit.
Hereinafter, a configuration and its operation when a pipeline structure is introduced into the barrel shift device of Patent Document 1 will be described in detail with reference to FIG. 10.
FIG. 10 is a schematic diagram illustrating the barrel shift device of Patent Document 1 with a pipeline structure introduced thereinto. A first shift circuit 10 performs a shift process with respect to input data based on a first control signal, and outputs the resultant data as intermediate data 30. Here, the first shift circuit 10 is composed of a 1-bit left-shift circuit 11, a 2-bit left-shift circuit 12, and a 4-bit left-shift circuit 13 to achieve an arbitrary shift ranging from a 7-bit left shift to a 0-bit shift.
An intermediate data holding circuit 30 holds and outputs the intermediate data which is an output of the first shift circuit 10 to a second shift circuit next thereto.
A control signal holding circuit 40 holds and outputs a second control signal.
The second shift circuit 50 performs a shift process with respect to the intermediate data based on the second control signal output by the control signal holding circuit 40, and outputs the result as output data. Here, the second shift circuit 50 is composed of an 8-bit left-shift circuit 51 and a 16-bit right-shift circuit 52. By combining the shift processes of the first and second shift circuits, an arbitrary shift ranging from a 15-bit left shift to a 16-bit right shift is achieved with respect to input data.
Patent Document 1: Japanese Patent Unexamined Publication No. 2000-293354 (page 7, FIG. 1)